Flatworm transmitted to humans in fresh contaminated water.
Eggs shed in feces or urine Hatch in fresh water Develop into cercaria in snails Penetrate human skin (dermatitis) Migrate to portal blood/mesenteric veins/venous plexus and mate (serum sickness like illness 4-8 weeks after skin invasion can see lymphadenopathy and hepatosplenomegaly) Eggs produced and circulate in venous blood through liver Released to intestines/bladder to expel and infect more hosts
Chronic disease you see granulomatous/fibrotic changes in the liver/bladder due to eosinophils and reaction to deposited eggs
Infected mosquitoes bite humans Inject sprozoites Replication in liver Merozoites released and infect erythrocytes Asexual replication Lysis and release of merozoites (illness like fever and periodic symptos of anemia, hemaglobinuria)
Pt are jaundiced hypotensive have hepatosplenomegaly and tachycardia with fever. Can have complications like cerebral malaria, immune complex deposition in glomerulus
Challenges to preventing parasitic diseases?
Widespread, large and impossible to eradicate (for example, all mosquitos)
DDT used but can gain resistance and has bad side effects
Antimalarials (doxycycline, mefloquine)
Public Health strategies for controlling schistosomiasis
building wells/latrines, providing potable water, preventing contamination of environmental water, education about disease, use of molluscides to control snail hosts and treatment with drugs like praziquantel. Vaccination?